U.S. patent number 5,192,328 [Application Number 07/778,704] was granted by the patent office on 1993-03-09 for knee joint replacement apparatus.
Invention is credited to Thomas F. Winters.
United States Patent |
5,192,328 |
Winters |
* March 9, 1993 |
Knee joint replacement apparatus
Abstract
During the course of a total knee replacement, at least one and
preferably a number of different low friction members having
rotated artificial surfaces of different rotated angles are
provided in order to determine the appropriate angle and
displacement of the artificial prominence and plateaus on the low
friction members, so that the appropriate low friction member may
thereafter be permanently installed during the total knee
replacement in order to recreate the optimal position.
Inventors: |
Winters; Thomas F. (Winter
Park, FL) |
[*] Notice: |
The portion of the term of this patent
subsequent to October 22, 2008 has been disclaimed. |
Family
ID: |
27022722 |
Appl.
No.: |
07/778,704 |
Filed: |
October 18, 1991 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
414804 |
Sep 29, 1989 |
5059216 |
|
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Current U.S.
Class: |
623/20.31 |
Current CPC
Class: |
A61F
2/38 (20130101) |
Current International
Class: |
A61F
2/38 (20060101); A61F 002/38 () |
Field of
Search: |
;623/18,20 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Green; Randall L.
Assistant Examiner: Willse; D.
Attorney, Agent or Firm: Allen, Dyer, Doppelt, Franjola
& Milbrath
Parent Case Text
This is a division of application Ser. No. 07/414,804 filed Sep.
29, 1989, now U.S. Pat. No. 5,059,216.
Claims
What is claimed is:
1. Apparatus for replacing a removed portion of the upper end of a
human tibia, the apparatus comprising:
a bearing member, the bearing member, the bearing member having a
central longitudinal prominence emulating the natural eminence of
the tibia and outward, low friction bearing surfaces on either side
of the central prominence for engaging opposing bearing surfaces of
the femur and thereby function as the upper end of the tibia; and
wherein the bearing member is structured such that, upon
implantation,
the direction of the central prominence is rotated at an angle on
the order of between 3.degree.-15.degree. with respect to the
longitudinal direction across the cut of the tibia at the level of
the removed portion.
2. The apparatus recited in claim 1 wherein the bearing surfaces
comprise recessed portions, with one recessed portion on either
side of the central prominence of the bearing member, each recessed
portion adapted to receive a femoral bearing surface.
3. The apparatus recited in claim 1 wherein the bearing surfaces
comprise two recessed portions each on opposite sides of the
central prominence, the two recesses being rotated substantially as
the central prominence and displaced in a direction from the
posterior to the anterior to optimize correct knee motion.
4. The apparatus recited in claim 1 wherein the angle of rotation
of the central prominence is leftwardly for a left knee and
rightwardly for a right knee.
5. The apparatus recited in claim 4 wherein the bearing member
along one side of the central prominence is asymmetric with respect
to the other side.
Description
BACKGROUND OF THE INVENTION
The present invention relates generally to apparatus and related
methods for repairing or replacing deteriorated joints, and is
especially adapted for use in repairing or replacing the human knee
joint.
The joint of the human knee is formed by the low friction and
movable contact between the femur (thigh bone) and the tibia (shin
bone). The upper extremity of the tibia has a surface defined by a
generally centrally located prominence, referred to as the
intercondular eminence, extending generally longitudinal in the
direction of joint motion, the eminence fitting within a
corresponding groove in the distal femur. The tibial bearing
surface includes a pair of tibial plateaus on opposite sides of the
longitudinal eminence which are adapted to act as bearing surfaces
for the two ball-shaped bearing surfaces on opposite sides of the
femoral groove, called the "femoral condyles". The articulations of
the femur and tibia are held together in a movable relationship by
the knee cap (patella), and ligaments and muscles extending both
inside and outside of the knee, with soft fluidic, cushioning
tissue extending between the bearing surfaces.
Frequently, a deteriorated knee requires the replacement of the
bearing surfaces of the upper portion of the tibia and the lower
portion of the femur; this is customarily referred to as a "total
knee replacement". Because a total knee replacement involves the
cutting away of a substantial portion of the upper portion of the
tibia and the lower portion of the femur and with replacement of
those two portions with artificial components, then these
artificial components must employ low friction surfaces which are
capable of cooperating together to simulate as closely as possible
the natural movement of the human knee before surgery.
A total knee replacement usually involves the removal of
approximately between 0.5 to 1.5 centimeters of the upper portion
of the tibia, including both the longitudinal eminence and the
tibial plateaus, leaving a relatively flat surface into which a
rigid metal support member is inserted. Then, a low friction
bearing member is affixed to the support member, with the low
friction member including a longitudinal prominence simulating the
eminence and with bearing surfaces simulating the tibial plateaus.
A lower end portion of the femur is then removed, and a member
having bearing surfaces replicating the femoral condyles is then
affixed to the remaining end of the femur.
SUMMARY OF THE INVENTION
The present invention is based upon the discovery and observations
that the rotation of the naturally occurring tibial plateau may not
be replicated in the bearing surface of the artificial low friction
member, which may hinder the natural movement of the knee.
Accordingly, there has been devised a method for providing a number
of low friction insert members having different rotational
relationships, so that during the course of a total knee
replacement, different low friction members having rotated
artificial surfaces of different rotated angles may be installed
upon the support member. The knee is then moved through a range of
motion to determine the appropriate angle and displacement of the
artificial prominence and plateaus, and thereafter permanently
installing a member having the appropriate rotational disposition,
thereby recreating the optimal position.
Accordingly, the present invention also contemplates a prosthesis
for replacing the proximal aspect of the tibia, with the prosthesis
comprising a member with a low friction surface having a
longitudinal prominence designed to simulate and replace the
natural eminence extremity of the tibia. It will of course be
understood that the longitudinal prominence of the bearing member
surface is centrally dispose, with two recessed portions on either
side of the prominence adapted to receive a femoral bearing
surface, with the two recesses being rotated substantially as the
longitudinal prominence of the prosthesis and displaced in an
anterior or posterior direction to optimize correct knee
motion.
Generally, the angle of rotation of the longitudinal prominence of
the prosthesis is leftwardly for a left knee and rightwardly for a
right knee, with the angle of rotation being on the order of
between 3.degree.-15.degree., although other rotational
displacements may be appropriate in certain cases. It will be
understood from the above discussion regarding the method of the
present invention that a number of prostheses with different
specific rotational displacements will be provided, so that the
appropriate rotational displacement can be selected during the
course of the surgery.
THE DRAWING
FIG. 1 is a perspective view of the top portion of the human tibia
before a total knee replacement operation.
FIG. 2 is a front elevation of a human tibia after implantation of
a prior art total knee prosthesis.
FIGS. 3, 4 and 5 are top plan, front and side views, respectively,
of a prior art bearing surface prosthesis like that illustrated in
FIG. 2.
FIGS. 6, 7 and 8 are top plan, front and side views, respectively,
of a tibial bearing surface insert for a left knee in accordance
with the present invention.
FIGS. 9, 10 and 11 are top plan, rear and side elevations,
respectively, of an insert for a right knee in accordance with the
present invention.
FIG. 12 is a front view of the tibia and femur after a total knee
replacement using the method of the present invention.
DETAILED DESCRIPTION OF THE DRAWING
A preferred embodiment of the present invention will now be
described with reference to the drawings.
FIG. 1 illustrates the upper extremity of a human tibia 10, which
includes a tibial eminence 12. The shape and dimensions of the
eminence 12 vary, of course, from individual to individual.
Nevertheless, the eminence generally extends in a longitudinal
direction defined by dotted line 14 between the front and rear of
the tibia. A pair of tibial plateaus 16, 18 are positioned on
opposing sides of the eminence 12, and are adapted to receive the
ball-shaped bearing surfaces at the lower extremity of the femur
(see, for example, the artificial bearing surfaces 74 and 76
attached to the femur 70 in FIG. 12). The tibial plateaus 16, 20
are defined by an outer peripheral edge 20.
Dotted line 22 in FIG. 1 lies in a plane approximately where a cut
is typically made during a total knee operation, in order to remove
the upper portion of the tibia 10. Of course, when the upper
portion is removed, the eminence 12, ridge 20 and plateaus 16, 18
are removed as well. The resulting cut across the plane defined by
line 22 generally lies on the order of between 0.5 and 1.5
centimeters below the top of the tibia, in the direction of the
tibia tubarcle 26. The cut is usually flat across the tibia 10. It
has been discovered that the longitudinal direction across the cut
at about line 22 results in a significant displacement in the
longitudinal direction between the front and rear of the tibia
across the cut, as is illustrated by the dotted line 24. This
angular displacement is caused by the change in the rotational
disposition of the tibia downwardly toward the tibial tubarcle 26
from the upper extremity of the tibia 10.
In the prior art, as shown in FIGS. 2-5, it has been customary to
affix a support member 32 to the cut surface as defined by line 22,
with the support member 32 having a peg 36 extending into the tibia
10 to fit the prosthesis to the bone. The surface 34 of the member
32 is dimensioned to receive a low friction member 38. The prior
art arrangements for the low friction member 38 include a
longitudinal prominence 40 which extends longitudinally front to
rear (see FIG. 3), and a pair of recessed areas 42, 44 which
simulate the tibial plateaus 16, 18 and are adapted to provide a
low friction surface for the artificial femur bearing surfaces 74,
76 attached to the femur 70 as part of a total knee replacement
(FIG. 12), As shown in FIGS. 3-5, the prior art bearing member may
include a rear indentation and ridges 43, 45 which surround the
respective plateaus 42, 44.
Low friction bearing members 50, 50A in accordance with the present
invention will now be described with reference to FIGS. 6-8 and
9-11, respectively. The arrangement shown in FIGS. 6-8 is designed
for use with a left knee, and the arrangement of FIGS. 9-11 is
designed for use with a right knee. In FIGS. 6-8 and 9-11, common
reference numerals are utilized for the same drawing elements.
The perspective bearing member 50, 50A includes a front surface 53,
53A and a rear surface 55, 55A. An offset longitudinal prominence
52, 52A extends angularly between the front and rear of the bearing
member 50, 50A at a respective angular displacement which may be
determined during the course of a total knee operation, as
described in greater detail below (or which may determine
pre-operatively through the use of CT scanning techniques). That
angular displacement is shown by the angular arrow 56, 56A between
the longitudinal line 14 and another dotted line 54, 54A. Each of
the bearing members 50, 50A includes a first recess portion 58, 58A
and a second recessed portion 60, 60A designed to simulate the
tibial plateaus 16, 18 of the tibia 10 (FIG. 1). Each recessed
portion 58, 58A, 60, 60A has a respective ridge 59, 59A, 61, 61A
surrounding the recess. As noted above, the angular displacement
reflected by angle 56, 56A is typically on the order of between
about 3.degree.-15.degree., although other angles may be utilized
in certain cases. It is contemplated that a number of bearing
members for a left knee and a number of bearing members for the
right knee having different angular configurations would be
provided in advance of a total knee operation, so that the surgeon
may select the appropriate angular displacement during the course
of the operation. Alternatively, CT scans prior to the operation
may be utilized to define the optimal angle of rotation for the
prosthesis member 50, 50A.
A total knee surgical procedure of course exposes the upper end of
the tibia 10. Thereafter, a lateral cut is placed across the top of
the tibia 10, generally in the plane of line 22 (FIG. 1), to remove
a small portion of the upper end of the tibia 10 at the knee. The
removed portion includes the natural eminence 12 and the bearing
surfaces 16, 18 for the femoral bearing surfaces. Thereafter, the
support member 32 is be fixed to the cut surface. A prosthesis,
such as bearing member 50 in FIG. 12, is temporarily installed upon
the support member 32. The longitudinal prominence 52 of the
bearing member 50 is rotated at a substantial angle with respect to
the longitudinal direction of the tibia 10 across the cut surface
22 as is described above. After insertion of a first bearing member
having a particular angular displacement for the longitudinal
prominence 52, the tibia is then moved to determine knee motion for
correctness of the rotation of the angle. If the angle is
inappropriate, another bearing member 50 is selected and the
process continued until the proper angular displacement is
achieved. Thereafter, the bearing member 50 is permanently
installed. As is shown in FIG. 12, it would also be customary to
remove a portion of the femur 70 including a portion of its natural
bearing surfaces, and the installation of an artificial femoral
bearing surface 72, 74 which is separated by a groove 80
dimensioned to mate with and receive the rotated longitudinal
prominence 52.
In a significant number of cases, the rotated longitudinal
prominence of the present invention will result in a substantial
improvement in the function of the joint after a total knee
operation.
* * * * *